Volume 93, Issue 4

A highly efficient synthesis of new chiral bisphosphanes derived from the renowned NORPHOS ligand is presented. The synthesis involves ring-opening metathesis of NORPHOS dioxide with an external olefin, followed by saturation of the new double bonds and adjustment of the oxidation level of phosphorus centers oxidation level. The synthesized bisphosphanes retain the configuration and enantiomeric purity of the starting NORPHOS. Their utility as ligands in asymmetric catalysis is exemplified using an open -NORPHOS ligand in some benchmark Rh-catalyzed hydrogenations of enamides where excellent chemical yields and enantiomeric purities of the products have been secured. The proposed protocol demonstrated the possibility of a straightforward synthesis of new chiral catalysts to be utilized in the asymmetric synthesis of pharmaceutically important compounds, such as amino acid derivatives.

The large and significant increase in carbon dioxide concentration in the Earth’s atmosphere is a serious problem for humanity. The amount of CO 2 is increasing steadily which causes a harmful greenhouse effect that damages the Earth’s climate. Therefore, one of the current trends in modern chemistry and chemical technology are issues related to its utilization. This work includes the analysis of the possibility of chemical consumption of CO 2 in Diels-Alder processes under non-catalytic and catalytic conditions after prior activation of the C=O bond. In addition to the obvious benefits associated with CO 2 utilization, such processes open up the possibility of universal synthesis of a wide range of internal carboxylates. These studies have been performed in the framework of Molecular Electron Density Theory as a modern view of the chemical reactivity. It has been found, that explored DA reactions catalyzed by Lewis acids with the boron core, proceeds via unique stepwise mechanism with the zwitterionic intermediate. Bonding Evolution Theory (BET) analysis of the molecular mechanism associated with the DA reaction between cyclopentadiene and carbon dioxide indicates that it takes place thorough a two-stage one-step mechanism, which is initialized by formation of C–C single bond. In turn, the DA reaction between cyclopentadiene and carbon dioxide catalysed by BH 3 extends in the environment of DCM, indicates that it takes place through a two-step mechanism. First path of catalysed DA reaction is characterized by 10 different phases, while the second by eight topologically different phases.

The effect of the template nature and modification with MnO x on the catalytic efficiency of Ce 0.8 Zr 0.2 O 2 (CZ) in oxidation of CO (2 vol% CO and 1 vol% O 2 in He, pulse feeding) and soot particles (tight contact between soot and catalyst, TGA/DSC) was analyzed. The CZ catalysts were prepared using the CTAB and sawdust (SD) templates and modified with Mn (8 wt%) by wet impregnation followed by calcination at 400 °С. SEM-EDS, XRD, Raman and photoelectron spectroscopy, N 2 adsorption, EPR, TPR-H 2 and catalytic tests results demonstrated better catalytic activity of CZ(SD) in CO oxidation than of CZ(CTAB) because of the biomorphic texture, higher structural defectiveness and improved oxygen mobility of the former catalyst. Low surface reducibility and low concentration of active oxygen species on the CZ(SD) surface deteriorated its catalytic efficiency in the topochemical reaction of soot oxidation. Despite the different structure and degree of interaction between MnO x and CZ, the Mn-modified catalysts showed the similar catalytic properties: much better than of both unmodified catalysts in CO oxidation and worse than of CZ(CTAB) in soot oxidation. Mn 2+ ions incorporated better into the surface layer of CZ(SD) than of CZ(CTAB), for which the inhomogeneous distribution of MnO x and decreased specific surface area were observed.

In recent years the transformations of fructose and glucose to the platform chemical 5-hydroxymethylfurfural (5-HMF) have been studied extensively, and a variety of mechanisms have been proposed. This review summarizes the varied mechanisms proposed and methods used to study the dehydration of biomass, such as fructose and glucose, to give 5-hydroxymethylfurfural. For fructose dehydration, two main mechanisms have been suggested including a cyclic and an acyclic pathway, of which the cyclic pathway dominates. The conversion of glucose to 5-HMF can proceed either through initial isomerization to fructose or a direct dehydration. For glucose to fructose isomerization, two main reaction pathways have been proposed (1,2-hydride shift and enolization). This review discusses the mechanisms that have been determined based on the evidence from experiments and/or calculations, and briefly introduces the techniques frequently used in such mechanistic studies. Mechanisms in this field are strongly dependent on the nature of the solvent and the catalyst used, so it is important that researchers have a general idea about the existing mechanisms, and the methods and techniques used for investigation, before pursuing their own mechanistic studies.

The XXI st century might be called the Plastic Era. With the continually growing consumption and production, low recycling level, one observes the continuous transformation of the Blue Planet into the Ocean of Plastics. Among various problems related to the presence of synthetic materials in the environment, the ghost nets draw particular attention. They are present in the global ocean due to lost or abandoned fishing gear. Their impact on the environment is represented by the tones of animals caught. Moreover, they are an abundant source of secondary marine microplastic and release a considerable amount of toxic chemical compounds. To resolve this issue, an interdisciplinary approach is needed. Chemical research enables a better understanding of polymer behaviour and their weathering, whereas spectroscopy helps in qualitative analyses and proposes solutions. This paper aims to present the interdisciplinary study of this phenomenon and its broad context, including social awareness but underlines the crucial role of chemical research. One focuses on the basic studies of chemical and physical properties as this knowledge provides the first and essential step to tackle the problem.

Over the recent decades, conducting polymers have received great interest in many fields including microelectronics, energy conversion devices, and biosensing due to their unique properties like electrical conductivity, stability, and simple synthesis. Modification of conducting polymers with noble metals e.g. gold enhances their properties and opens new opportunities to also apply them in other fields like electrocatalysis. Here, we focus on the synthesis of hybrid material based on polyindole (PIN) nanobrush modified with gold nanoparticles and its application towards electrooxidation of ethanol. The paper presents systematic studies from synthesis to electrochemical sensing applications. For the characterization of PIN–Au composites, scanning electron microscopy and X-ray diffraction analyses were used. The electrocatalytic performance of the proposed hybrid material towards alcohol oxidation was studied in alkaline media by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy techniques. The results show that PIN–Au hybrid can be employed as an effective and sensitive platform for the detection of alcohols, which makes it a promising material in electrocatalysis or sensors. Moreover, the proposed composite exhibits electrocatalytic activity towards ethanol oxidation, which combined with its good long-term stability opens the opportunity for its application in fuel cells.